[cfe-dev] JSONCompilationDatabase additional keys

[Manuel Klimek]

On Sat, Sep 14, 2013 at 8:31 AM, Sean Silva <silvas at purdue.edu> wrote:

>
>
>
> On Fri, Sep 13, 2013 at 5:59 AM, Manuel Klimek <klimek at google.com> wrote:
>
>> On Thu, Sep 12, 2013 at 3:07 AM, Sean Silva <silvas at purdue.edu> wrote:
>>
>>>
>>>
>>>
>>> On Wed, Sep 11, 2013 at 8:14 AM, Manuel Klimek <klimek at google.com>wrote:
>>>
>>>> On Wed, Sep 11, 2013 at 12:41 PM, Nicholas Gill <mythagel at gmail.com>wrote:
>>>>
>>>>> Hello cfe-dev,
>>>>>
>>>>> At present unknown keys in the compile_commands.json file will cause
>>>>> the JSONCompilationDatabase parser to reject the file.
>>>>>
>>>>> 1. Would a patch to relax this constraint be accepted?
>>>>> 2. Would other consumers of the compile_commands.json be negatively
>>>>> impacted by unknown keys?
>>>>>
>>>>
>>>> Yes. This can be rather big, and being able to quickly parse it is
>>>> important for interactive use cases.
>>>>
>>>>
>>>
>>> I don't think that this is a very good reason. Parsing the compilation
>>> database in the JSON format is going to take O(project size) work, and
>>> anything O(project size) is not going to be adequate for interactive use
>>> cases anyway.
>>>
>>
>> How do you come to that conclusion? I've run benchmark on chromium-sized
>> projects, and the interactive use-case worked just fine.
>>
>>
>
> On my machine it takes 30ms to parse the compile_commands.json for
> clang/llvm (measured with perf(1)). Typically interactive response time
> expectation is 100ms, so 30ms is about 1/3 of the total time available,
> which IMO is unacceptable. Conversely, a project >3x larger would be
> noninteractive.
>

Have you made sure it scales linearly?
If your analysis is true, it has regressed, and we should fix the YAML
parser.
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